本篇文章给大家带来的内容是关于python3中setdefault的用法介绍（代码） ，有一定的参考价值，有需要的朋友可以参考一下，希望对你有所帮助。
当字典 d[k]找不到正确的键时,Python会抛出异常,有没有一种优雅的方法来避免这种情况呢?答案是肯定的.
index0.py 从索引中获取单词出现的频率信息,并写入列表 --没有使用dict.setdefault
#!/usr/bin/env python
# coding=utf-8
import sys, re
WORD_RE = re.compile(r'\w+')
index = {}
with open(sys.argv[1], encoding='utf-8') as fp:
for line_no, line in enumerate(fp, 1):
for match in WORD_RE.finditer(line):
word = match.group()
column_no = match.start()+1
location = (line_no, column_no)
occurrences = index.get(word, [])
occurrences.append(location)
index[word] = occurrences
for word in sorted(index, key=str.upper):
print(word, index[word])zen.txt
The Zen of Python, by Tim Peters Beautiful is better than ugly. Explicit is better than implicit. Simple is better than complex. Complex is better than complicated. Flat is better than nested. Sparse is better than dense. Readability counts. Special cases aren't special enough to break the rules. Although practicality beats purity. Errors should never pass silently. Unless explicitly silenced. In the face of ambiguity, refuse the temptation to guess. There should be one-- and preferably only one --obvious way to do it. Although that way may not be obvious at first unless you're Dutch. Now is better than never. Although never is often better than *right* now. If the implementation is hard to explain, it's a bad idea. If the implementation is easy to explain, it may be a good idea. Namespaces are one honking great idea -- let's do more of those!
执行 python3 index0.py zen.txt
a [(19, 48), (20, 53)] Although [(11, 1), (16, 1), (18, 1)] ambiguity [(14, 16)] and [(15, 23)] are [(21, 12)] aren [(10, 15)] at [(16, 38)] bad [(19, 50)] be [(15, 14), (16, 27), (20, 50)] beats [(11, 23)] Beautiful [(3, 1)] better [(3, 14), (4, 13), (5, 11), (6, 12), (7, 9), (8, 11), (17, 8), (18, 25)] break [(10, 40)] by [(1, 20)] cases [(10, 9)] ...
index.py 使用了dict.setdefault 只用了一行就解决了获取和更新单词的出现情况列表
#!/usr/bin/env python
# coding=utf-8
import sys, re
WORD_RE = re.compile(r'\w+')
index = {}
with open(sys.argv[1], encoding='utf-8') as fp:
for line_no, line in enumerate(fp, 1):
for match in WORD_RE.finditer(line):
word = match.group()
column_no = match.start()+1
location = (line_no, column_no)
index.setdefault(word, []).append(location)
for word in sorted(index, key=str.upper):
print(word, index[word])也就是说:
my_dict.setdefault(key, []).append(new_value)
等价于
if key not in my_dict:
my_dict[key] = []
my_dict[key].append(new_value)二者效果相同,只是setdefault只需一次就完成整个操作,而后者需要进行两次查询
台讯电子企业网站管理系统 简繁全功能版
下载
超级适合代理建设企业站点的企业源码，超方面实用！程序说明： 1.特色：简繁中文切换、产品展示系统、新闻发布系统、会员管理系统、留言本计数器、网站信息统计、强大后台操作 功能等； 2.页面包括：首页、企业介绍、滚动公告通知发布系统、企业新闻系统、产品展示系统、企业案例发布展示系 统、企业招聘信息发布系统、信息资源下载系统、在线定单系统、在线客服系统、在线留言本系统、网站调查投票系统、友情连接系统、会
在Python中操作字典之setdefault()方法的使用
立即学习“Python免费学习笔记（深入）”；
